Automatic batch weigher



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. Gem/d Cr /1401 ATTORNE S United States Patent 3,528,518 AUTOMATICBATCH WEIGHER Gerald C. Mayer, Wayne, N.J., assignor to Howe RichardsonScale Company, Clifton, N.J., a corporation of Delaware Filed Aug. 3,1967, Ser. No. 658,229 Int. Cl. G01g 19/22 US. Cl. 177-70 16 ClaimsABSTRACT OF THE DISCLOSURE The batch weighing system disclosed hereinfor successively weighing out preselected ingredients in a batch formulahas a modularized weight controller circuit in which preset voltagescontrol the weights of ingredients or materials making up the batch andin which a skeleton network is selectively built up by using logic cardmodules to provide selected combinations of the following functions:automatic, compensated cutoff of each ingredient delivered to the scalehopper, delivery of each ingredient to the scale hopper at a full flowfeed rate and a dribble feed rate, overweight and underweight checkingof each delivered ingredient, partial batch control for delivering onlya selected percentage of each ingredient to reduce the total weight ofthe batch while retaining the proper proportions of the ingredients in agiven formula, an automatic tare to facilitate the use ofnon-accumulative weight selection devices, and a maximum batch sizecontrol to provide an indication if the scale capacity is exceeded.

FIELD OF INVENTION This invention relates to electrical controlequipment wherein a measurable condition is sensed and compared with areference signal to provide a control signal representative of thedeviation between the sensed condition and the reference signal. Thepresent invention is particularly concerned with the incorporation ofsuch equipment into batch weighing systems wherein preset voltagecircuits control the weights of different materials making up a batchformula.

BACKGROUND Conventional automatic batch weighing systems, such as thatdescribed in United States Letters Patent No. 3,173,504 issued to M. T.Thorsson et al. on Mar. 16, 1965, typically comprise a transducer forproducing a signal representing the weight of material delivered to aweighing hopper, a preset weight selection device for producing separatereference signals respectively representing the preselected weights of aplurality of materials to be successively delivered to the weighinghopper, a control circuit for comparing the weight selection signal withthe transducer signal to control the amount of each material deliveredto the hopper, and a programmer for auto matically delivering thematerials in succession and for sequentially switching in thecorresponding weight selection reference signals.

The electrical circuitry employed prior to this invention for theforegoing type of batch weight control is relatively complex, contains aconsiderable number of electrical components, and requires a great dealof hand wiring as evidenced from Pat. No. 3,173,504 mentioned above.Manufacture of such a control circuitry is therefore costly andtime-consuming. These prior control circuits furthermore are relativelyinflexible in that the removal or addition of many of the functionsperformed by the circuit adversely affects the performance of theremaining circuitry. Consequently, the addition or removal of suchcontrol circuit functions is attainable only by making major revisionsin the circuitry.

ice

Integrated and modularized circuits offer significant advantages whichif properly adapted can avoid the shortcomings mentioned above. However,it will readily be appreciated that many circuits are not adapted formodularization and integration owing to their logic and the form of theelectrical components in the circuit.

Modularization of a circuit and the placement of the modules on logiccards, which are adapted to be plugged into a motherboard, thereforedepend upon a number of factors including the logic of the circuit andthe components which are employed to make up each module. Logic, as usedin the foregoing sense, involves the relationship of the modules to eachother, to other unmodularized portions of the circuit, and to externalcircuits which are electrically connected to the modularized circuit.

Prior to this invention, no suitable logic has been devised tomodularize a major portion of a batch weight control circuit, especiallywhen various, interrelated refinements are involved such as dribble feedcontrol, compensated final cutoff control, overweight and underweightchecking, automatic taring, partial batch control, and maximum sizebatch control.

OBJECTS AND SUMMARY OF INVENTION It therefore is a major object of thisinvention to provide a novel modularized control circuit which isespeciall adapted for use in a batch weighing system.

For batch weight control two basic signals are delivered to the controlcircuit of this invention. One is the scale output signal which isdeveloped by a transducer and which represents the weight of materialdelivered to the scale hopper. The other is the weight selection signalwhich is developed by a weight selection device and which represents thedesired or preselected amount of material to be delivered. The controlcircuit compares these signals to produce an output error signal whichis operative upon reaching a predetermined value to perform a certainfunction, such as cutting oif the delivery of the material to theweighing hopper.

These scale output and weight selection signals are delivered toseparate input terminal connections in the control circuit. Each inputterminal connection, according to one aspect of this invention, isconnected by parallel current paths to a plurality of separate terminalswhich may be in the form of sockets in a motherboard. The socket ormotherboard terminals are arranged in pairs, one for delivering thescale output signal and the other for delivering the weight selectionsignal.

The modules, which delevop the output signals of the control circuit areon separate logic cards, which are adapted to be plugged into themotherboard for connection to one or more of the socket terminal pairsmentioned above. Thus each module receives the scale output and weightselection signals independently of any of the other modules whichdevelop the output signals of the control circuit. Their insertion intoor removal from the control circuit therefore does not affect theperformance of the other parts of the circuit.

Accordingly, the control circuit of this invention provides for theselective addition or subtraction of func-- tions simply by plugging inor unplugging the logic cards. The circuit may be built up with logiccard modules to independently and optionally perform any one or combination of functions including dribble feed rate control, compensatedfinal cutoff control, overweight checking and underweight checking.

With dribble feed rate control, the feed rate of material beingdelivered to the weighing hopper is automatically reduced to a dribbleflow rate as a balanced scale condition is approached to minimizeweighing errors. One card may be used to provide the dribble feed and tocontrol the final cutoff of the material when a balanced scale conditionis reached. Under such circumstances, the dribble feed control may beomitted simply by replacing the logic card module with one having onlythe final cutoff control.

The control circuit of this invention also can be used in conjunctionwith non-accumulative weight selection devices and accumulative weightselection devices. In the former, the preset voltage signals arerespectively proportional to the weights of the ingredients. Forexample, if it is desired to deliver 80 pounds of a first ingredient and60 pounds of a second ingredient, the voltage signals developed by anon-accumulative weight selection device and sequentially delivered tothe control circuit will each be proportional to their associatedingredients such as 8 volts for the first ingredient and 6 volts for thesecond ingredient. In comparison, the voltage signals developed by anaccumulative weight selection device for the same weights will be 8volts for the first ingredient and 14 volts for the second ingredient.

When a non-accumulative weight selection device is used, it is necessaryto tare the scale output by effectively cancelling out the transducerscale output signal before each succeeding ingredient is delivered. Thelogic of the control circuit of this invention is such that an auto-tarelogic card module may be plugged in or unplugged without adverselyaffecting other parts of the circuitry that would be used in conjunctionwith an accumulative weight selection device.

In conjunction with the non-accumulative weight selection device, amaximum batch control card module may optionally be incorporated toprovide an indication if the preset weight of each ingredient to bedelivered to the weighing hopper exceeds the scale capacity or resultsin what is termed as an impossible batch.

In addition to the foregoing, a partial batch control is readily addedto or removed from the control circuit with no significant change incircuitry.

Thus the present invention contemplates and has as a further object anovel, versatile batch weigher control circuit in which variousfunctions can be added or subtracted without affecting the overallperformance of the system. Another more specific object of thisinvention is to provide a novel modularized batch weight control circuitwhich can be built up with logic cards to perform selected combinationsof the following functions: automatic, compensated final cutoff ofmaterial feed to the weight hopper, automatic dribble feed control ofthe material being delivered, underweight checking, overweight checking,automatic taring to facilitate the use of non-accumulative weightselection devices, maximum batch control, and partial batch control.

Still another object of this invention is to provide a novel auto-tarecircuit which is simple and inexpensive.

A further object of this invention is to provide a novel auto-tare andmaximum size batch control combination wherein a signal developed by theauto-tare circuitry is applied with the weight selection signal and acontrol signal to provide an indication if the selected amount ofingredient to be delivered exceeds the scale capacity.

Another object of this invention is to provide a novel, simplifiedpartial batch control circuit which enables an operator to selectivelyreduce the size of the batch while retaining the proper proportions ofthe ingredients making up the batch formula.

Further objects of this invention will appear as the descriptionproceeds in connection with the appended claims and annexed drawingswherein:

FIG. 1 is a generally diagrammatic view illustrating an automatic batchweighing apparatus constructed according to a preferred embodiment ofthis invention;

FIGS. 2A and 2B diagrammatically illustrate the weight controllercircuit shown in FIG. 1;

FIG. 3 is a partially schematic view illustrating the logic card andmotherboard arrangement for the modules shown in FIG. 2;

FIG. 4 illustrates the weight control circuit modification foreliminating the dribble feed control shown in FIG. 2;

FIG. 5 illustrates the weight control circuit modification foreliminating the partial batch control shown in FIG. 2;

FIG. 6 is a diagram of the sequencing and switching circuit illustratedin FIG. 1; and

FIG. 7 is a diagram of the energizing circuits for the material feedmotors shown in FIG. 1.

BATCH WEIGHING APPARATUS Referring now to the drawings wherein the samereference numerals designate like parts throughout, the weighingapparatus of this invention shown in FIG. 1 comprises a hopper 20 havingand open bottom 22 for discharging a first fluent or particulatematerial in a layer upon an endless belt, power driven feeder 24 ofconventional construction. Feeder 24 has an upper belt flight 26 whichis horizontal and which moves from left to right in FIG. 1 betweenpulleys 28 and 30. An electric motor 32 connected to pulley 30 by anendless chain 34. drives pulleys 28 and 30 at the same constant speed. Amanually operated discharge gate 36 is provided to control delivery ofmaterial from hopper 20 to feeder 24. The material passing through theopen bottom 22 of hopper 20 is advanced in a layer on the upper beltflight 26 of feeder 24. This material falls off the end of the flight asit passes around pulley 28 and descends in a freely falling continuouscolumn directly into a weigh hopper 38. In this embodiment, feeder 24 isemployed to deliver material to hopper 38 at a full flow rate and aseparate feeder 40 is used to deliver a dribble feed to the weighhopper.

Feeder 40 preferably is of the same construction as feeder 24 and has aconveyor belt comprising an upper flight 42 which moves horizontallyfrom right to left in FIG. 1 between two pulleys 44 and 46. Pulleys 44and 46 are driven at the same constant speed by an electric motor 48which is connected to pulley 46 by an endless chain drive 50. A fixedhopper 52 having an open bottom 54 positioned over feeder 40 dischargesmaterial by gravity onto belt flight 42. Hopper 52 is provided with aconventional manual operated discharge gate 56 for controlling deliveryof material to feeder 40.

With continued reference to FIG. 1, the material discharged by hopper 52and advanced by belt flight 42 to the end of feeder 40 above weighhopper 38 falls off belt flight 42 as it passes around pulley 44 anddescends in a freely falling column directly into the hopper.

In the construction shown in FIG. 1, the relative positions of feeders24 and 40 are only diagrammatically illustrated and, in practice, feeder40 may be positioned beside feeder 24 to provide a more compactassembly. In such case, it is clear that hopper 52 may be an extensionor part of hopper 20.

To deliver a second material to weigh hopper 38, separate full flow anddribble flow feeders 60 and 62 are provided. Feeders '60 and 62 may beof the same construction as feeders 24 and 40* as shown in FIG. 1.Accordingly, the parts of feeders 60 and 62 which are the same as theparts in feeders 24 and 40 have been designated by like referencecharacters sufiixcd with the letter a.

While the material feeding apparatus described herein is limited to thedelivery of two ingredients to weigh hopper 38, it will be appreciatedthat any number of ingredients may be delivered to hopper 38 by addingfurther feeding apparatus of the type already described. It also will beappreciated that any other suitable arrangement of feeding may beemployed. Also other types of material feeding apparatus may be employedsuch as, for example, screw conveyors.

As shown in FIG. 1, weigh hopper 38 is provided with a discharge gate 66for controlling the discharge of material through the open bottom ofhopper 38 by gravity.

Gate 66 is opened and closed by a suitable fluid motor 68. A valve 70actuated by a solenoid 72 controls the supply and exhaust of fluid foroperating motor 68. When solenoid 72 is energized, motor 68 is operatedto open gate 66. Deenergization of solenoid 72 causes gate 66 to close.

With continued reference to FIG. 1, a pivotally mounted full flow catchgate 73 is interposed between feeder 24 and hopper 38. Gate 73 is swungabout its pivot axis between its full line and dotted line positions torespectively permit and interrupt delivery of material from feeder 24 bya suitable fluid motor 74. A valve 75 actuated by a solenoid 76 controlsthe supply and exhaust of fluid for operating motor 74. When solenoid 76is energized, motor 74 is actuated to cause gate 73 to open permittingfeeder 24 to deliver material to hopper 38.

As shown in FIG. 1, a further pivotable catch gate 77 is interposedbetween feeder 40 and hopper 38. Gate 77 is swung between its full lineand dotted line positions by a suitable fluid motor 78 to permit andinterrupt delivery of material from feeder 40. A valve 79 actuated by asolenoid 80 controls the supply and exhaust of fluid for operating motor78. When solenoid 80 is energized, motor 78 is actuated to cause gate 77to open permitting feeder 40 to deliver material to hopper 38.

Feeders 60 and 62, as shown in FIG. 1, are also provided with catchgates and fluid motor operators of the same construction as justdescribed for feeders 24 and 40. Accordingly, the catch gate structurefor feeders 60 and 62 have been identified with like reference numeralssuflixed with the letter a as shown.

A force transducer 100, which is operatively connected to the weighingapparatus, may be of any suitable form, such as a load cell or apotentiometer device, for sensing the weight of material delivered tohopper 38 and for converting the sensed weight into an analogue, DCvoltage signal.

In this embodiment, transducer 100 is shown to comprise at least oneload cell 101 operatively connected to hopper 38. The load cell may beof the conventional silicon or resistance gauge type and is excited froma suitable D.C. supply source 102. For a silicon gauge load cell, theexcitation source may be *-15 volts as shown to provide a full scaleoutput of 1 volt for 30 volts ex citation. Load cell 101, of course, maybe connected to any suitable, operative scale part which moves inproportion to the weight of delivered material such as, for example, afulcrumed weigh beam (not shown) connected to hopper 38 or the dialshaft in a standard dial head scale 102a. Such a scale dial head isdescribed in United States Letters Pat. No. 3,254,728 bearing the issuedate of June 7, 1966.

WEIGHT CONTROLLER CIRCUIT Referring now to FIG. 2A, the output oftransducer 100 is applied to a terminal 104 of a summing resistor 103 ina weight controller circuit 106. Circuit 106, as will be explained indetail shortly, is, among other things, operative to electricallycompare the voltage output signal of transducer 100 with successivelyimpressed, preset reference voltage signals each representing thedesired weight of a material which is to be delivered to hopper 38. Thiscomparison is employed to develop control signals for controlling theamount of each material delivered to hopper 38 and also for providingother functions including overweight, underweight, and acceptable weightindications in a che-ckweighing operation. The preset reference voltagesignals are provided by a weight selection circuit 107 which will bedescribed in detail later on.

As shown in FIG. 2A, the transducer output signal applied to terminal104 is coupled through resistor 103 to a junction 104a which isconnected to an input channel of a signal conditioning, operationalamplifier 108. A variable feedback resistor 110 couples the outputvoltage signal of amplifier 108 back to junction 104a to provide for anadjustment of the voltage range impressed upon circuit 106. Operatingpower for amplifier 108 is derived from source 102.

A zero tare adjustment is provided by a potentiometer 112 having an arm113 which is adjustable along a resistor 114. Resistor 114, according toone aspect of this invention, is connected across source 102. Thevoltage impressed on arm 113 is coupled through a summing resistor 115to junction 104a as shown. The force transducer output voltage signaland the zero tare potentiometer voltage signal will be opposite in sign.

Arm 113 is adjusted to offset the weight of scale parts acting ontransducer to provide a zero amplifier output voltage signal at junction104b when hopper 38 is empty.

The values of resistors 103 and 115, which forms a summing network, areequal and the value of resistor is adjusted to provide an output voltageat junction 104b which is proportional to the algebraic summation of thevoltage signals applied to terminal 104 and arm 113 respectively. Sincethe sign of the potentiometer voltage signal applied to arm 113 isopposite with respect to the sign of the transducer voltage signalapplied to terminal 104, the voltage signal at junction 104b willtherefore be proportional only to the amount of material delivered tothe weigh hopper.

Where resistors 104, 110, and respectively have values R R and R andwhere the voltages at terminal 104, arm 113, and junction 104b arerespectively represented by E, E and E it will be observed that E E i EE is substantially equal to The reason for this is that for theillustrated amplifier connections, the maximum voltage at junction 104awill only be a very small and negligible amount greater or less thanground or zero volts owing to the very high gain and impedancecharacteristics of operational type amplifiers.

Both transducer 100 and amplifier 108 are suitably located at the scalewhich comprises hopper 38 and dial head 102a. The remaining componentsof circuit 106, which will now be described, may be remotely located ata control panel (not shown).

With reference to FIGS. 2A and 2B, the remainder of circuit 106 isformed by a series of integrated modularized building blocks comprisinga filter module 120, a pair of dual comparator modules 121 and 122, asumming amplifier module 123, an auto-tare module 124, a maximum batchsize module 125, and a pair of voltage follower modules 126 and 127.Each of the modules -127 is on a printed-circuit logic card 134 (seeFIG. 3) which is adapted to be plugged into a motherboard 135 or thelike. Modules 120127 represent a complete control system with allrefinements, but as will be seen later on, many of these modules, owingto their unique, interrelated arrangement and connections in thecontroller circuit, may optionally be removed or added without affectingthe overall performance of the weighing system. The network comprisingamplifier 108, potentiometer 112, and the associated resistors also maybe incorporated into aprinted logic card. Any suitable conventionalplug-in card and motherboard assembly may be employed for modules120-127.

As shown in FIG. 2A, the amplified output voltage signal of amplifier108 is delivered to module 120 which filters out any A.C. component thatmay have been superimposed on the DC. signal. The filter of module 120may be of any suitable form and should be of the low pass type havinggood frequency and time response characteristics to develop a filteroutput signal which is substantially free of AC. components that mightinterfere with the trouble-free operation of circuit 106.

The filtered and amplified transducer voltage output signal E isconnected by a conductor 139 from the output of module to an inputterminal 284 (FIG. 2B) in module 121. Terminal 284 is connected througha summing resistor 141 to a summing junction 140. Also coupled tojunction are auto-tare and weight selection voltage signals E and Ewhich are delivered along conductors 142 and 143 respectively. Conductor142 is connected to an input terminal 286 in module 121, and terminal286 is connected through a summing resistor 144 to junction 140.Similarly, conductor 143 is connected to a terminal 285 in module 121,and terminal 285 is connected through a summing resistor 145 to junction140. The manner in which the auto-tare and weight selection signals aredeveloped will be described shortly.

Also coupled to junction 140 is a preset dribble feed voltage signal E,which is developed on the adjustable arm 146 of a potentiometer 148having a resistor 150 connected across source 102. Arm 146 is connectedthrough a summing resistor 151 to junction 140. Junction 140 isconnected to the inverting channel of an operational amplifier 152 inmodule 121. The non-inverting channel of amplifier 152 is clamped toground. Operating power for amplifier 152 is derived from source 102.

Amplifier 152, resistors 141, 144, 145, and 151, and a 10 volt Zenerdiode 153 form a voltage comparison circuit whose output signal controlsenergization of a dribble feed relay DEP-S. Diode 153 has its anode gateand cathode gate respectively connected to junction 140 and the outputof amplifier 152 to provide a feedback loop for controlling the gain ofthe amplifier.

As shown, the cathode gate of diode 153, the output of amplifier 152,and one terminal of ,the operating coil of relay DEP-S are connected tojunction 158. The other terminal of the coil of relay DEP-S is connectedto a +10 volt source.

When the algebraic summation of signals E E E and E is negative, diode153 will be reverse biased and will hold the output voltage at junction158 at 10 volts. This is evident from the fact that for a very smalldifference between the signal voltages applied to the amplifierinverting and non-inverting input channels or terminals, an operationaltype amplifier produces its maximum output voltage which is positive ornegative depending upon the direction of the dilference. This is due tothe very high impedance and gain characteristics of operational typeamplifiers. Thus, when the algebraic summation of signal voltages E E Eand E is at least slightly negative, amplifier 152 tends to produce amaximum positive voltage since junction 140 is connected to theinverting channel.

The voltage at junction 140, owing to the circuitry of operationalamplifiers, will not deviate significantly from zero volt when amplifier152 is grounded as shown in FIG. 2B, regardless of the deviation of thealgebraic summation of signal voltages E E E and E, from zero volt.Since the slightest deviation of the algebraic Summation of voltages E EE and E; from zero is negative and since the amplifier output voltage ispositive, diode 153 will therefore be reverse biased and Will hold thevoltage at junction 158 to 10 volts, for, as previously mentioned, it isa 10 volt Zener.

When +10 volts is applied at junction 158, there will be no voltage dropacross the coil of relay DEP-S. Relay DEP-S will therefore bede-energized. When the algebraic summation of signal voltages E E E andE becomes zero, diode 153 becomes forward biased to clamp the voltage atjunction 158 to substantially Zero volt. As a result, a voltage drop isdeveloped to energize relay DEP-S.

Amplifier 152 is conventional and preferably is of the single swing typeshown and described on page 45 of the Burr-Brown Research CorporationHandbook (first edition) entitled Operational Amplifiers.

Module 121, as shown in FIG. 2B, is provided with a further summingjunction 160 and a second operational amplifier 162. Conductors 139,142, and 143 are respectively connected to terminals 157, 161, and 159on module 121, and terminals 157, 159, and 161 are respectivelyconnected through summing resistors 165, 166, and 167 to junction 160.The voltage signals E E and B are therefore applied to junction 160respectively through resistors 165, 167, and 166. A preset weightcompensating voltage signal E developed by sequencing shift register 164is also impressed on junction 160. Junction 160 is connected to theinverting input terminal of amplifier 162. The non-inverting inputterminal of amplifier 162 is clamped to ground. As Will be explained indetail later on, voltage signal E compensates for the additionalmaterial which is fed to the hopper as a result of lags in the system.These legs unavoidably delay cutoff of the material when a balancedscale condition is reached.

Comparator 162 has a feedback loop containing a 10 volt Zener diode 163.This comparator circuitry comprising amplifier 162, diode 163, andresistors 165, 166, and 167 is the same as that just described foramplifier 152, diode 153, and resistors 141, 145, and 144. When thealgebraic summation of signals E E E and E becomes zero, diode 163 isforward biased to provide a voltage drop across the coil of a finalcutoff relay EPS. Relay EP$ will therefore be energized. As will bedescribed fully later on, energization of relay EP-S interrupts thedribble feed of the material to hopper 38. When the algebraic summationof signals E E E and E is negative, diode 163 is reverse biased toprevent a voltage drop across the coil of relay EP-S. In thesecircumstances, relay EP-S will be de-energized.

As shown in FIG. 2A, weight selection circuit 107 is shown to comprise aplurality of potentiometers 170' corresponding in number at least to thenumber of different ingredients to be delivered to hopper 38 in a singlebatch. In this embodiment, two weight selection potentiometers areshown, but more may be added if needed. The resistors of potentiometers170 are respectively designated by the reference characters 171 and 172which are connected in parallel across one terminal of a voltagedropping resistor 173 and the +15 volt terminalpf source 102. The otherterminal of resistor 173 is connected to the 15 volt terminal of source102. The value of resistor 173 is so chosen that the voltage at itsterminal connected to resistors 171 and 172 is zero. This, as willbecome apparent shortly, provides signal E, with a sign which isopposite with respect to the sign of signal E Thus, if signal E ispositive, signal E will be negative.

The adjustable potentiometer arms or wipers for resistors 171 and 172are respectively designated by the reference characters 174 and 175 andare respectively connected to fixed contacts in a bank 177 of asequencing shift register 180'. Register 180 forms a part of a suitablemulti-deck stepper switch 182 having a contact arm 184 which isadvanceable to successively engage contacts in bank 177.

Potentiometers 170 are preset to impress on arms 174 and 175 negativeweight selection signal voltages which are respectively proportional tothe selected weights of the different ingredients to be delivered tohopper 38 in a batching operation. These weight selection voltagesignals are successively transmitted to arm 184 as arm 184 is stepped tosuccessively engage the contacts in bank 177. The weight selectionvoltage signal delivered to stepper arm 184 is coupled to the input ofmodule 126.

In this embodiment, potentiometers 170 are set to providenon-accumulative weight signals as compared with a cumulative weightselection which is Well known in the art. In the latter type of weightselection, the weight of the second ingredient is added to that of thefirst ingredient to provide a signal or factor which is equal to the sumof the weights of the first and second ingredients to control the cutoffof delivery of the second ingredient. By

removing module 124 and resetting potentiometers 170, accumulativeweight selection is attained. This mode of Weight selection isdisadvantageous because weighmg errors will have a cumulative effect toupset the proportions of ingredients still to be weighed in a givenbatch. An example of cumulative weight selection is provided in theaforementioned Pat. No. 3,254,728.

In contrast to cumulative weight selection, weighing errors attributableto ingredients already weighed in accordance with the preset valuesprovided by potentiometers 170 do not affect the proportion of weight ofingredients still to be delivered because of the algebraic summation ofthe auto-tare signal E mainly with signals E and E As a result, thevoltage signal applied to arm 184 is proportional to the desired weightof each ingredient and not to the summation of the desired weight of thematerial being delivered and the weights of materials already delivered.

In place of the potentiometer form of weight selection disclosed in thisembodiment, alternate forms of weight selection devices may be employedsuch as, for example, formula capsules, patchboards, card readers,digital computer inputs, and analog computer inputs.

Still referring to FIG. 2A, the voltage follower module 126 comprises anoperational amplifier 190 with a feedback loop 192 coupling the outputvoltage back to the input of the amplifier. A suitable voltage followerof this type is shown on page 9 of the previousl mentioned Burr-Brownhandbook. This voltage follower circuit in essence transfer a highimpedance source to a low impedance output. In this connection, weightselection circuit 107 has a relatively high impedance, and the voltagefollower is incorporated into controller circuit 106 to reduce thesignal impedance being delivered to the comparator modules 121-123.Operating power for amplifier 190 is derived from source 102 as shown,and the gain of amplifier 190 will be positive. This output voltagesignal is connected to a partial batch control potentiometer 198. Theresistor 196 of potentiometer 198 is connected between ground and thesignal output terminal of amplifier 190. The arm 195 of potentiometer198 is connected to the input terminal of a further voltage followeramplifier 202 in module 127.

When arm 195 is moved to a position where no part of the potentiometerresistance is connected in series between the output of amplifier 190and the input of amplifier 202, 100 percent of the voltage signaldeveloped at the output of amplifier 190 will be impressed on the inputof amplifier 202. As arm 195 is moved down toward the potentiometerterminal that is connected to ground, the percentage of the voltageoutput signal impressedon arm 195 and thus coupled into amplifier 202will reduce in accordance with the ratio of the resistance value betweenarm 195 and ground and the total resistance of the potentiometer. Inthis manner, the weight selection settings of potentiometers 170' can bemodified to deliver to hopper 38 a properly proportioned percentage ofthe ingredients making up the batch to be weighed out simply byadjusting arm 195. In addition, the partial batch potentiometer can beemployed to vary only the weights of selected ingredients if desired.

The voltage follower module 127 advantageously is of the same form asmodule 126 and is desired owing to the relatively high impedance sourcecreated by potentiometer 198. The output of module 127 is connected toconductor 143 to couple the weight selection voltage signal E which isdeveloped by circuit 107, to junctions 140 and 160' as previouslydescribed. Since arm 184 is connected to the non-inverting inputterminal of amplifier 190 and since the output of amplifier 190 isconnected to the non-inverting input terminal of amplifier 202, theoutput signal E will be negative.

As shown in FIG. 2A, the auto-tare module 124 is a sample or track andhold network comprising an operational amplifier 206, a unity gainfeedback resistor 208,

and a storage capacitor 210. Capacitor 210 is connected between theinput and output channels of amplifier 206 in parallel with resistor 208when a set of normally open contacts TR-Cl are closed. Terminal 212 ofresistor 208 is connected to an input resistor 214. Terminal 212 also isconnected through contacts TR-Cl to one plate of capacitor 210 and tothe input channel of amplifier 206. This circuitry is conventional asshown on page 99, FIG. 3.75, of Philbrick Researches, Inc., Handbook(second edition) entitled Applications Manual for Computing Amplifiersfor Modelling Measuring Manipulating and Much Else.

According to one aspect of this invention, the output of filter moduleis connected to one terminal of resistor 214 by a conductor 216. Theopposite terminal of resistor 214, as previously mentioned, is connectedto terminal 212 of resistor 208. The output of amplifier 206, the otherterminal 217 of resistor 208, and the correspond ing plate of capacitor210, which is connected to terminal 217, are all connected to conductor142 by a branch conductor 218. The voltage signal E developed byautotare module 124 therefore is transmitted to junction along a currentpath which is in parallel with the voltage output from module 120.

The function of the track and hold auto-tare module 124 is to providevoltage signal E with such a value that it effectively cancels outvoltage signal E when the delivery of each material is started. At thebeginning of each feed cycle, therefore, the unbalanced weight selectionvoltage signal E is impressed upon the comparator circuits in module 121for developing a negative algebraic summation.

When contacts TR-Cl are closed by energizing a relay TR-C, the amplifiedand filtered transducer output voltage signal E is applied to terminals284 and 157 without uncoupling the connection of module 120 to terminals286 and 161. Since closing of contacts TR-Cl couples resistor 208 backto the input of amplifier 206, the amplifier gain will be unity. Theoutput of amplifier 206 Will thus be equal in magnitude but opposite insign to the amplified and filtered transducer output voltage signal EWhen contacts TR-Cl are closed, capacitor 210 will continually becharged up to thus track the output voltage signal of module 120 andconsequently memorize the voltage signal being delivered to module 124.

Upon opening contacts TR-Cl, capacitor 210- Will produce a voltage tothe input of amplifier 206 which is equal to that last encounteredbefore the contacts opened. Before each ingredient is delivered tohopper 38 in accordance with the weight settings provided by weightselection circuit 107, contacts TR-Cl are closed to track and memorizethe transducer output voltage signal E and then are opened to hold thetracked signal. Operation of contacts TR-Cl is controlled by sequencingand switching circuit 156 in a manner which will be described in detaillater on.

Considering the operation of the circuit thus far described, assume, asan example, that a residue having a weight equivalent to 1 volt atmodule 121 is in hopper 38, that the weight of a first ingredient whichis preset by arm 174, is equivalent to 8 volts, and that the weight of asecond ingredient, which is preset by arm 175, is equiva lent to 6volts.

Before delivery of the first ingredient is initiated by starting feeder24, circuit 156 is operated to energize relay TR-C. Contacts TR-Cl willtherefore close to allow capacitor 210 to be charged. After sufiicienttime is allowed for charging capacitor 210 up to the input voltage (1volt), relay TR-C is de-energized to open contacts TR-Cl before feeder24 is started.

Stepper arm 184 will be in engagement With the first contact in bank 177and the partial batch potentiometer arm will be at its maximum positionfor coupling 100 percent of the voltage signal from module 126 to module127. Therefore, signal E will be equal to 1 volt, signal E will be equalto 1 volt, and signal E will be equal to 8 volts.

At some time before the full amount of the first ingredient is deliveredto hopper 38, the control circuitry is capable of reducing the flow ratefrom the full feed flow provided by feeder 24 to a dribble feed, thelatter being provided by feeder 40. The transfer point from full feed todribble feed is controlled by selectively adjusting arm 146 to somevalue such as +2 volts. For the circuitry in this embodiment, signals Eand E are required to have opposite signs.

At the moment the feeding cycle is initiated by starting feeder 24,voltage signals E E E and E will be equal to +1 volt, -1 volt, -8 volts,and +2 volts respectively. Signals E and E cancel each other out toeffectively tare the scale and thereby eliminate any weighing errorsattributable to the residue remaining in hopper 38. This leaves signalsE and E; which produce, at the start of the feeding cycle, a deviationof 6 volts. Relay DEP-S is therefore de-energized, and circuit 156 isoperated to actuate feeders 24 and 40 in a manner to be described indetail later on.

As material enters hopper 38 from feeder 24, the trans ducer voltagesignal E increases, but the remaining signals E E and E remain constant.The change in am plitude of signals E (i.e., AE will therefore reducethe algebraic summation of signals E E E and E When this summation isreduced to zero volts, relay DEP-S will become energized in the mannerdescribed previously. Circuit 156, as will be described in detail lateron, responds to the energization of relay DEP-S to stop feeder 24.Operation of feeder 40 will continue, thus commencing the desirable feedcycle.

A weight of the first ingredient equivalent to 6 volts has now beendelivered to hopper 38. This leaves a weight equivalent to 2 volts to bedelivered by the dribble feeder 40.

Sequencing shift register 164, which develops voltage signal E may be ofthe same form as circuit 107. Accordingly, like reference numeralssuffixed by the letter a have been applied to designate like elements.

Stepper arm 184a is ganged to arm 184 so that both arms are advancedconcomitantly to engage corresponding contacts in their respectivecontact banks. Thus when arm 184 engages the first contact in bank 177,arm 184a engages the first contact in bank 177a. Potentiometer arms 174aand 175a are preset to control cutoff of the dribble feed of the firstand second ingredients to be de livered in a given batch.

Arm 174a is set to develop a voltage signal which will provide for adesired amount of compensation and which will be opposite in sign withrespect to voltage signal E This voltage signal, which is signal E andwhich for this example may be +1 volt, is coupled through a summingresistor 233 to junction 160 so that when the dribble feeder 40 isstarted signals E E E and E will respectively be +7 volts (1 voltrepresenting the residue plus 6 volts representing the amount of thefirst ingredient delivered by feeder 24), --1 volt (owing to the storedcharge on capacitor 210), +8 volts, and +1 volt. The algebraic summationof these signals will therefore equal 1 volt, and diode 163 will bereverse biased. As a result, relay EPS will be de-energized which is thecondition required to maintain operation of feeder 40.

As material is delivered by feeder 40, the algebraic summation ofsignals E E E and E reduces and when it becomes zero, diode 163 becomesforward biased to cause energization of relay EP-S. This will occur whenthe scale output signal E reaches 8 volts, which amounts to 1 volt ofresidue and 7 volts of the first material delivered by the operation offeeders 24 and 40. Circuit 156 responds to energization of relay EP-S toclose gate 77 and to stop motor 48.

Owing to the unavoidable time delay involved in swing ing catch gate 77to its material interrupting position and in stopping feeder 40 afterrelay EP-S is energized, an additional amount of material will bedelivered to hopper 38 before actual cutoff occurs. This additionalamount of material is predetermined by checking operation of theweighing apparatus before actual usage and in this example is a weightequivalent to 1 volt as applied at terminal 157. Potentiometer arm 174a,having been set for this amount, therefore delivers a voltage signal of+1 volt to compensate for the additional material entering hopper 38after relay EP-S is energized.

The final amount of material delivered to hopper 38 will therefore beequivalent to the selected 8 volts, and the transducer output voltagesignal E applied to conductor 139 will therefore rise to +9 volts. Thecompensation values for the ingredients making up the batch may be setat different values depending upon various factors such as the densityof the ingredients.

If no compensation were provided for, it will be appreciated that anadditional amount of material in excess of the desired or selectedweight will be fed to hopper 38 owing to the inherent electrical andmechanical lags in the weighing system.

Circuit 156 next re-energizes relay TR-C to again close contacts TR-Cfor charging capacitor 210 up to the level of signal E which is now at 9volts. Before feeder 60 is started for delivering the second ingredientto hopper 38, relay TR-C is de-energized and the stored capacitor chargeis impressed on the two comparator circuits in module 121 to effectivelycancel out signal E in the manner previously described.

When stepper arm 184 is now advanced to the second contact in bank 177,an unbalanced voltage signal (E of 6 volts is applied to the twocomparator circuits in module 121. Circuit 156 is operated by thiscondition to start feeders 60 and 62 for delivering the secondingredient to hopper 38 at a full flow feed rate.

With voltage signal E set at +2 volts, the algebraic summation of theapplied signals will be reduced to zero when voltage signal E reaches alevel of +13 volts. Operation of feeder 60 will consequently be stoppedand operation of the dribble feeder 62 will continue.

When stepper arm 184 was advanced to the second contact in bank 177, arm184a also was advanced to the second contact in bank 177a. The dribblefeed is thus carried out and when the algebraic summation of theimpressed voltage signals E E E and E reduces to zero, circuit 156 isoperated to cutoff the flow of material and to stop motor 48a. Theforegoing cycle is repeated for as many ingredients which were selectedto make up the formula.

In this embodiment, the values of resistors 141, 144, 145, and 151 areequal. Likewise, the values of resistors 165, 166, 167, and 233 are alsoequal.

If the operator desires only a certain percentage of either the firstingredient or the second ingredient, he simply adjusts the potentiometerarm 195 to reduce the magnitude of voltage signal E If in the examplejust given arm 195 is adjusted to the midpoint of resistor 196, voltagesignal E will be reduced from 8 volts to 4 volts for the firstingredient and from 6 volts to 3 volts for the second ingredient.

The maximum batch size module is operative to provide an alarm or othersuitable indication if the amount of the ingredient to be delivered whenadded to the amount of material already in hopper 38 exceeds the hopperor scale capacity. Module 125, as shown in FIG. 2, comprises a summingjunction 230 and an operational amplifier 232. A voltage signal Edeveloped on the arm 234 of a potentiometer 236 is coupled through asumming resistor 237 to junction 230. A conductor 238 connected betweenterminals in modules 124 and 125 applies voltage signal E through asumming resistor 239 to junction 230. Similarly, a conductor 240 whichmay be connected directly to conductor 143 couples voltage signal Ethrough a summing resistor 241 to junction 230.

Junction 230 is connected to an input terminal of amplifier 232 whichmay be of the same form as amplifier 152. Operating power for amplifier232 is derived from source 201. A feedback loop containing a 10 voltZener diode 242 is connected between junction 230 and the outputterminal of amplifier 232. Amplifier 232, diode 242, resistors 237, 239,and 241, and junction 230 constitute a voltage comparator network of thesame form as the comparator circuit in module 121.

An alarm relay MBE-S has its coil terminals respectively connected to a10 volt source and the output termi nal of amplifier 232. The resistorof potentiometer 236 is connected across a suitable source of DC.voltage and arm 234 is adjusted to develop a positive voltage levelrepresentative of the maximum weight of material that the scale canhandle.

Since auto-tare module 124 intermittently tracks the transducer outputvoltage signal, signal E which is negative, represents that amount ofmaterial already in hopper 38 after contacts TR-Cl have been closed andthen opened following the delivery of the last ingredient. The weightselection voltage signal (E for the next ingredient to be delivered willbe impressed on junction 230 when stepper arm 184 is advanced to thenext contact. Since signal E is also negative, the algebraic summationof signals E and E wil provide a negative signal representing the amountof material which will be in hopper 38 if the next ingredient is added.If the summation of signals E and E is less than the positive value ofvoltage signal E diode 242 is forward biased to develop a voltage dropfor energizing relay MBE-S.

If the summation of voltage signals E and E is greater than voltagesignal E indicating that the capacity of the scale will be exceeded whenthe ingredient represented by voltage signal E is delivered, theresulting algebraic summation of signals E E and E becomes negative withthe result that diode 242 becomes reverse biased to de-energize relayMBE-S. De-energi'zation of relay MBE-S closes a set of normally closedcontacts MBE-Sl to operate an alarm 244, alerting the operator to thefact that he has an impossible batch. Alarm 244 may be connected acrossany suitable voltage source such as source 102.

In addition to the dribble feed and final cutoff control provided bymodule 121, module 122 may be added to indicate whether the amount ofeach ingredient delivered to hopper 38 is overweight, underweight, orwithin an acceptable, preset range. The circuitry and logic of module122 is the same as that of module 121 except that the latter has apotentiometer 250 in place of the sequencing shift register 164. Likereference numerals suffixed by the letter a have therefore been appliedto designate corresponding elements in module 122.

The underweight limit and the overweight limit of an acceptable weightrange are set by adjusting potentiometers 148a and 250 respectively.

The connections of module 122 to conductors 139, 142, and 143 is thesame as that described for module 121. Voltage signals E E and E willtherefore be applied through their associated summing resistors tojunctions 140a and 160a. In addition to these signals, a voltage signalE7 is impressed on potentiometer arm 146a which is connected throughresistor 151a to junction 140a. 'Ihe algebraic summation of signals E EE and B, will thus control the voltage at the output terminal 158a ofamplifier 152a.

Junction 158a is connected to one terminal of an operating coil for anunderweight relay UEP-S. The other coil terminal of relay UEP-S isconnected to a +10 volt source as shown. An overweight relay OEP-S hasone coil terminal connected to a +l' volt source; the other coilterminal being connected to a junction 255 in module 122. Junction 255is also connected to the output of amplifier 162a and to the cathodegate of diode 163a.

If, for example, an underweight equivalent to 1 volt is acceptable,potentiometer arm 146a is set to a position where signal E equals +1volt. Considering the previous example in which the residue weight wasselected as 1 volt and the weight of delivered material was 8 volts, thevoltage signal E will equal +9 volts. Before contacts TR-Cl are closedto track this increased transducer output voltage level, signal E is 1volt, thus providing a change in signal E (AE which is equal to +8 voltsas a result of completing the delivery of the first ingredient to hopper38. The weight selection voltage E; at this stage will still equal 8volts because stepper arm l84 has not, as yet, been advanced from thefirst contact to the second contact in bank 177. Therefore, thealgebraic summation of signals E E E and B, will be +1 volt. If thedraft of the first ingredient is overweight, by any amount, thisalgebraic summation remains positive. If the draft of the firstingredient is underweight by the permissible amount of 1 volt, thealgebraic summation of voltage signals E E E and B; will be zero volts.Therefore the underweight condition will be satisfied if this algebraicsummation does not go negative. If, for example, the draft of the firstingredient weighs less than the amount equivalent to 7 volts, thealgebraic summation of signals E E E and E goes negative to indicate anunderweight condition.

When the algebraic summation of signals E E E and E is positive or zero,indicating that the weight of the delivered material is not underweight,diode 153a is forward biased to cause a voltage drop across relay UEP4.As a result, relay UEP-S will be energized to operate contacts incircuit 156 for indicating a satisfactory condition. The operation ofcircuit 156 will be described later on.

If an insufficient amount of material is delivered to hopper 38 to causethe algebraic summation of signals E E E and E to go negative, diode153a will be reverse biased to hold +10 volts at junction 158a. RelayUEP-S will therefore be de-energized and the resulting inactivecondition will indicate an unsatisfactory underweight condition.

As shown in FIG. 2B, potentiometer 250' is connected across a suitablesource of DC voltage and has an adjustable wiper arm 254. Arm 254 isconnected to junction 160a and is adjusted to a position for determiningthe upper limit of the acceptable weight range. The voltage E impressedon arm 254 will be some negative value which is equivalent to themaximum, tolerable amount of material in excess of the preselectedamount developed by circuit 107.

For example, an excess amounting to 1 volt may be selected as beingacceptable. The voltage signal E will therefore be 1 volt. Operation ofthe overweight voltage comparison network of module 122 will now beexplained using the previous example in which voltage signal E wasselected as -8 volts and voltage signal E was as 1 volt owing to thepresence of residue prior to delivery of the first ingredient. Voltagesignal E developed by the track and hold operation of module 124, willbe 1 volt and will remain constant during delivery of the firstingredient to hopper 38.

If the weight of the first ingredient delivered to hopper 38 equals thepreselected amount, the change in voltage signal E will equal 8 volts sothat E will equal +9 volts which when algebraically summed up withsignals E E and E equals a value of 1 volt. Thus for any amount ofdelivered material which is equal or less than the selected amount (E3),the algebraic summation of signals E E E and E will be negative.

If the weight of delivered material is overweight by 1 volt, thealgebraic summation of signals E E E and E will, be zero. Therefore, forall weights of delivered material which are not overweight by theselected amount of 1 volt, algebraic summation of these signals will notgo positive. Under these conditions diode 163a will be reverse biasedand relay OEP-S will be de-energized.

If, on the other hand, the amount of material delivered to hopper 38exceeds the overweight limit of the acceptable weight range, say by 1volt, voltage signal E will become +11 volts which when algebraicallysummed with voltage signals E E and E results in a positive value. Thischange in polarity across diode 163a results in the energization ofrelay OEP-S in a manner similar to the operation described for relayUEP-S. Energization of relay OEP-S operates relay contacts in circuit156 to indicate an overweight condition. This sequencing circuitoperation will be described later.

Still referring to FIG. 2B, module 123 provides a readout signal for anover-under meter 259 of conventional form. This module comprises asumming junction 260 which is connected to the inverting input terminalof an operational amplifier 262. Conductors 139, 142, and 143 areseparately connected through summing resistors 263 to junction 260.Meter 259 is connected through and adjustable resistor 261 to a junction265 at the output of amplifier 262. A feedback loop containing aresistor 267 is connected between junctions 260 and 265. The other inputchannel of amplifier 262 is clamped to ground as shown. Operatingvoltage for amplifier 262 is derived from source 102. Module 123 thusconstitutes a voltage comparison circuit for signals E E and E Aftereach ingredient is delivered to hopper 38 and before contacts TR-Cl areclosed to track the increased transducer output signal E the algebraicsummation of voltage signals E E and E represents any deviation of thedelivered weight from the selected weight and also the direction (i.e.,either in an underweight or overweight direction) in which the variationoccurs. If the delivered weight is less than the selected weight, thevolt age at junction 265 will be positive, but if the delivered Weightis greater than the selected weight, the voltage at junction 265 goesnegative. Meter 259 may be of any suitable, conventional form whichresponds to such a signal variation.

The weight controller circuit just described offers significantadvantages which will now be considered in detail.

First, it is extremely compact and can be manufactured at comparativelylow cost. The particular interrelated arrangement of the logic cardmodules 12 -127 and their printed circuits significantly minimize theamount of hand wiring required as is evident from FIGS. 2A and 23. Costsand mistakes, consequently, are correspondingly reduced.

Second, the modularized weight controller circuit of this invention isexceptionally versatile in that the refinements including the auto-tare,maximum batch size control, partial batch size control, dribble feedcontrol, and overweight and underweight checking can each be added to orremoved from the circuit to form a new system without affecting theoverall performance of the system and without requiring any significantchanges in the basic circuitry. The versatility of the circuit in thisrespect is attributable to the unique manner in which the circuit isbuilt up with logic card modules from a basic or skeleton form and inwhich the logic card modules 120- 127 are arranged and related to eachother and to the non-modularized portions of the circuit. Alsocontributing to the versatility of the controller circuit is the factthat in the complete circuit, containing all the refinements andoptional features which were previously described, there is only one setof control and sequencing circuit contacts (contacts TR-Cl) between theinput and output interfaces of circuit 106. The input interface ofcircuit 106 is defined essentially by the connection of junction 104 totransducer 100 the connection of module 126 to circuit 107. The outputinterface of circuit 106 is defined by the dual outputs of modules 121and 122 to control operation of relays DEP-S, EP-S, UEP6, and OEP- S andthe outputs of modules 123 and 125 to control op- 16 eration of relaysMBES and meter 259. Examples of the changes that can be made will now beconsidered.

The logic card 134 containing the overweight and underweight dualcomparator module 122 may be removed from or added to circuit 106 simplyby unplugging the card or plugging it into motherboard 135. No changesin the remaining circuitry are required, and the addition or removal ofmodule 122 does not affect the functions performed by the remainingcircuitry and modules. The same applies individually to modules 123 and125.

If both dribble feed and automatic cutoff are not desired, the logiccard module 121 is simply unplugged from the motherboard. If automaticcutoff is desired, but dribble feed is not, a logic card containing amodified module 270 (see FIG. 4) may be plugged into the motherboard inplace of module 121.

As shown in FIG. 4, module 270 is the same as module 121 except that thevoltage comparisons circuit comprising resistors 144, 145, 141, and 151,junctions and 158, diode 153, and amplifier 152 have been eliminated,Accordingly like reference characters have been applied to designatelike components of the remaining circuitry, namely, junction 160, itsassociated summing resistors, amplifier 162, and diode 163. Operation ofrelay EP-S is still maintained under the control of amplifier 162 anddiode 163.

With module 270 plugged into the motherboard in place of module 121,operation of the system will remain the same except that the material ineach draft will be delivered to hopper 38 at one feed rate instead oftwo.

Of course, if compensation is not desired, it is only necessary toelectrically disconnect arm 184a from junction 160.

It is important to observe that the transducer scale output signal E andthe weight selection signal B are applied to separate input terminals incontrol circuit 106. From the scale input terminal, voltage signal E isdelivered along separate current paths to separate motherboard terminalconnection sockets schematically indicated at 280 in FIG. 23. There willbe one such terminal socket for each of the summing junctions 140, 160,140a, a, and 260.

Similarly, from the Weight selection input terminal, signal E isdelivered along the separate current paths to separate motherboardterminal connection sockets schematically indicated at 281. And therewill likewise be one such terminal connection for each summing junctionin each output module.

The output terminal of the auto-tare module 124 is also separatelyconnected to motherhood terminal socket connections indicated at 282 todeliver signal E along separate current paths to each summing junctionin each of the output modules.

Terminals 284, 285, 286, 157, 159, 161, 284a, 285a, 286a, 157a, 159a,and 161a are male plugs, and the sets of these male plugs, which arerespectively connected to junctions 140, 160, 140a, and 160a, are eachadapted to be plugged into a separate set of sockets 280-282 as shown.The male input terminals which are connected through resistors 263 tojunction 260 in module 123 are respectively indicated at 284b, 285b, and286b and are plugged into a separate set of sockets 280-282 on themotherboard. Similar plug and socket arrangements indicated at 287 areprovided for connecting relays DEP-S, EP-S, UEP-S, and 'OEP-S and meter259 to their respective modules. Plug and socket connections are alsoprovided for the other connections to modules 120, 124, 125, 126, and127 to provide the current paths shown in FIG. 2A. Ground voltagesource, and other connections are similarly effected by separate maleand socket connections. This unique arrangement is thus one of thefactors contributing to the versatility of the system.

The partial batch control provided by potentiometer 198 can readily beomitted from or left out of circuit 106 simply by electricallydisconnecting resistor 196 from the output of module 126, by unpluggingmodule 127 and by connecting a jumper 272 (see FIG. from the output ofamplifier 190 directly to conductor 143. Removal of potentiometer 198from circuit 106 eliminates the need for the voltage follower module127.

If it is desired to utilize an accumulative Weight selection device inplace of the non-accumulative weight selection circuit 107, it isnecessary to eliminate voltage signal E for voltage signal E willaccumulatively represent the desired weights of ingredients to bedelivered.

If, for example, the selected weight of a first ingredient is theequivalent of 8 volts and the selected weight of a second ingredient isthe equivalent of 6 volts, the magnitude of voltage signal E will be 8volts when delivery of the first ingredient is initiated and willincrease to 14 volts after the delivery of the first ingredient iscompleted and when delivery of the second ingredient is started. Thetransducer voltage signal E will be zero (assuming no residue) beforedelivery of the first ingredient is initiated and will increase toessentially 8 volts after delivery of the first ingredient is completedand before delivery of the second ingredient is initiated. Since signalsE and E are opposite in sign, a deviation of 6 volts (8 volts minus 14volts) will be impressed on module 121 and is the equivalent of theselected amount of the second ingredient, the level of signal Eincreases to 14 volts to reduce the deviation to zero. This, it will beappreciated, is a simplified example omitting the application of thedribble feed and compensation voltage signals.

When employing an accumulative weight selection device, the necessaryelimination of voltage signal E is achieved simply by unplugging thelogic card containing module 124 from the motherboard. The performanceof the remaining circuitry is not affected except for the function ofmodule 125. The maximum batch size control afforded by module 125,however, is not required, for the summation of the selected weights ofall the ingredients is directly obtainable from the accumulative settingof the weights on an accumulative type weight selection device.

From the foregoing, it will be appreciated that circuit 106 can readilybe built up from a skeleton network mainly comprising some form oftransducer signal conditioning equipment, such as amplifier 108,preferably a filter such as module 120, and a voltage follower, such asmodule 126 if the weight selection device has a high impedance. Theoutputs of modules 120 and 126 are then wired into the motherboard toprovide the previously described separate current paths extending fromthe output of each of the modules 120 and 126 to each summing junctionas well as the wiring to provide the separate current paths for signal Eto facilitate the optional use of the auto-tare module 124. Withessentially this basic circuitry, the variety of previously describedfunctions may optionally be performed.

It is also important to observe that circuit 106 is not necessarilylimited in application to weighing systems. In this connection,transducer 100 may be employed to sense other measurable conditions suchas temperature. Weight selection circuit then will be employed in abroader function, namely, that of settling up one or more control orcutoff points which may be used, for example, for controlling the sensedtemperature condition mentioned above.

Another important aspect of this invention resides in the use of acommon voltage source for all of the components which provide thepreviously described voltage signals E E In particular, it is to benoted that all of the equipment in circuit 106 is powered by source 102.Source 102 also provides the current for transducer 100, andpotentiometers 170 and 170a. As a result of this circuit arrangement,the comparisons of the various voltage signal combinations previouslydescribed are not materially affected by a drift in the power supplyvoltage.

Heretofore, it was the practice to employ power supply circuits whichhave a very stiff or stable characteristic to minimize errors resultingfrom drifting as caused, for example, by variations in the incoming linevoltage and/or variations in temperature. This invention eliminates theneed for such relatively stable power supply circuits by providing acontrol circuit which is capable of utilizing a common power supplysource. This is particularly important to achieve improved weighingaccuracy. Because of the common source 102, a power supply drift doesnot affect the relative values of signals E E E E E E and E SEQUENCINGAND SWITCHING CIRCUIT AND OPERATION Referring now to FIG. 6, circuit 156is shown in standby de-energized condition and comprises a pair ofconductors 300 and 301 across which a suitable source of DC. voltage iscoupled. To start the automatic operation of the weighing system, aspring-loaded, push-button start switch 304 is depressed to energize astart relay S-R. This circuit may be traced from conductor 300 throughclosed contacts of a discharge gate limit switch 306 through the closedcontacts of switch 304, and through the winding of relay S-R toconductor 301.

Switch 306 will be closed when discharge gate 66 is closed and will beopen when gate 66 is open. Thus, if switch 306 is open indicating thatgate 66 is open, relay SR cannot be energized.

Still referring to FIG. 6, energization of relay S-R closes two sets ofnormally open contacts S-Rl and S-R2. Closing of contacts S-Rlestablishes a holding circuit around switch 304 to maintain relay S-Renergized as long as discharge gate limit switch 306 remains closed.Closing of contacts S-R2 completes circuits for energiza relay TR-C anda slow pull-in delay feed timer The circuit for energizing timer DF-Tmay be traced from conductor 300, through contacts S-R2, through a setof normally closed contacts R-Tl of a slow drop-out re-set timer R-T andthrough the operating winding of timer DF-T to conductor 301. Thecircuit for energizing relay TR-C may be traced from conductor 300',through contacts S-RZ, through contacts R-Tl, through a set of normallyclosed contacts DF-Tl of timer DF-T, and through the energizing windingof relay TR-C to conductor 301.

By closing contacts TR-C1 (see FIG. 2A), the amplified and filteredtransducer output voltage signal E will be coupled to module 124 tocharge capacitor 210 to the value of signal E in the manner previouslydescribed. At this stage, no material has been fed to hopper 38. Inabsence of any residue in the hopper, therefore, the magnitude ofvoltage signal E will be zero, provided that potentiometer 112 has beenproperly adjusted to tare the weighing apparatus components acting ontransducer 100. If, on the other hand, there is residue in hopper 38,voltage signal E will have a finite magnitude representative of theweight of that residue. This voltage signal, which is steady owing tothe non-variation of the load in the hopper, will be stored and thusmemorized by capacitor 210.

After a short pre-determined period following energization of timer DF-Tand relay TR-C and permitting capacitor 210 to be charged up to thevalue of voltage signal E timer DF-T times out to open contacts DF-Tl,thereby de-energizing relay TR-C to cause contacts TR- C1 to open. Thestored value of the voltage signal on capacitor 210 will thus beproportional to the weight of any material in hopper 38 before anymaterial is delivered during the batch weighing operation. By timing outafter a preselected delay, timer DF-T closes a set a full flow motorstarter relay lFF and a dribble feed motor starter relay lDF if switch182 has been stepped of contacts DF-TZ to complete a circuit forenergizing to its first position where the contact arm 184 engages thefirst contact in bank 177.

In addition to the switch deck provided by arm 184 and its associatedcontact bank (FIG. 2A), switch 182 is provided with two further switchdecks 310 and 312 (FIG. 6). Deck 310 comprises a movable contact arm 314which is connected to a bus 316 and which is stepped to successivelyengage a series of electrically independent contacts in a bank 318. Thenumber of contacts in bank 318 preferably is the same as the number ofcontacts in the bank associated with arm 184.

Still referring to FIG. 6, deck 312 also has a movable contact arm 320which is connected to a bus 322 and which is stepped to successivelyengage a series of electrically independent contacts in a bank 324. Thenumber of contacts in bank 324 is the same as the number of contacts inbank 318. Both contact arms 314 and 320 as well as arms 184 and 184a arecoupled for unitary movement by a suitable linkage schematicallyindicated at 326.

As shown in FIG. 6, switch 182 comprises a conventional stepper switchnetwork 329 which includes the usual operating stepper coil SS-C andwhich also may include such circuit elements as a rectifier, arcsuppresser, and filter. Coil SS-C is connected across conductors 300 and301 'in a manner to be described more fully later on.

By energizing coil SS-C, contact arms 184, 184a, 314, and 320 arerespectively advanced in synchronism through the contact positions shownin the drawings. A number of the contact positions shown in the contactbanks for switch 182 are illustrated as open circuits for use if morethan two materials are desired to be fed to weigh hopper 38 in a singleweighing cycle.

The energizing circuit for relay 1FF may be traced through contactsS-R2, through contacts R-Tl, through contacts DF-T2, through a set ofnormally closed contacts DEP-Sl of relay DEP-S, through contact arm 320to the contact at the first position in bank 326', and through thewinding of relay lFF to conductor 301. Similarly, the energizing circuitfor relay 1DF may be traced through contacts S-RZ, R-Tl, and DF-T2,through a set of normally closed contacts EP-Sl of relay EPS, throughcontact arm 314 to the contact at the first position in bank 318, andthrough the winding of relay lDF-MS to conductor 301.

By energizing relay IFF, normally open contacts lFF- 1, 1FF-2, and 1FF-3are, as shown in FIG. 7, closed to complete a power circuit forenergizing motor'32. Energization of relay 1FF also closes a set ofnormally open contacts lFF-4 to energize solenoid 76. Energization ofsolenoid 76 opens catch gate 73 at the same time that motor 32 isstarted. Similarly, energization of relay 1DF closes normally opencontacts lDF-l, 1DF-2, and lDF- 3 to complete a power circuit forenergizing motor 48. Energization of relay lDF also closes a further setof normally open contacts '1DF-4 to energize solenoid 80'. Energizationof solenoid 80 opens catch gate 77 concomitantly with the energizatitonof motor 48.

As a result of starting motors 32 and 48, feeders 24 and 40 are actuatedto begin delivery of the first material to weigh hopper 38. Transducer100 senses this Weight addition to develop voltage signal E which iscompared with voltage signals E E and E in the manner previouslydescribed. As feeders 24 and 40 continue todeliver material to weighhopper 38, voltage E increases to approach a balanced signal conditionwhich is set by potentiometer 148 as previously explained.

When this balanced signal condition occurs, the voltage signal atjunction 158 decreases to zero to cause energization of relay DEP-S.Enerization of relay DEF-S opens contacts DEPS1 to interrupt theenergizing circuit for relay IFF. Consequently, relay IFF de-energizesto open contacts lF-F-l, l FF-Z, 1FF-3, and 1FF-4. As a result, motor 32will de-energize to stop feeder 24 and catch gate 73 will be moved toits flow-interrupting closed position.

Material now continues to flow into weigh hopper 38 but only at thereduced dribble feed rate from feeder 40. When the final cutoff pointset by potentiometer arm 174a is reached, the voltage signal at theoutput of amplifier 162 reduces to zero for energizing relay EP-S in themanner previously described. Energization of relay EP-S opens contactsEP-Sl to interrupt the energizing circuit for relay 1DF. De-energizationof relay lDF opens contacts lDF-l, lDF-Z, 1DF3, 1DF-4, Consequently,motor 48 will de-energize to stop feeder 40 and catch gate 77 will bemoved to its closed, flow-interrupting position. The delivery of thefirst material is therefore discontinued and the sequencing and controlcircuit 156 will then operate to prepare for and start the delivery ofthe second material.

With continued reference to FIG. 6, relay EP-S is provided with a pairof normally open contacts EP-SZ which close when relay EP-S energizes,signifying the completion of delivery of the first material, to completean energizing circuit for a slow pull-in scale stabilization timer DS-T.This circuit may be traced from conductor 300, through contacts S-RZ,TT1, DF-TZ, and EPASZ and through the operating winding of timer DS-T toconductor 301.

After a preselected time period sufficient to permit the scale tostabilize, timer DS-T times out to close contacts DS-Tl for completing acircuit from conductor 300 to a terminal 330 of an overweight andunderweight checking network 332. Network 332 comprises a set ofnormally closed contacts OEP-Sl and a set of normally open contactsOEP-SZ of relay OEPS, as well as a set of normally closed contactsUEP-Sl and a set of normally open contacts UEP-S2 of relay UEP-S. Inaddition, network 332 includes an off-weight alarm timer OWA-T.

As shown in FIG. 6, contacts OEP-Sl and UEP-S1 are connected in seriesin a branch circuit having one terminal connected to terminal 330 andthe other terminal connected to a terminal of the operating winding fortimer OWA-T. Contacts OEPS2 and UEP42 also are connected in series in aseparate branch circuit which is in parallel with the branch circuitcontaining contacts OEP- S1 and UEP-Sl.

When contacts DS-Tl close after the first material is received in hopper3'8 and the scale is permitted tostabilize, one of three conditions canexist: first, the weight of the first material received in hopper 38 iswithin the acceptable overweight and underweight limits set bypotentiometers 2.50 and 148a; second, the weight of the first materialreceived in hopper 38 is less than the underweight limit of theacceptable weight range as set by potentiometer 148a; and third, theweight of the first material fed to hopper 38 exceeds the overweightlimit of the acceptable weight range as set by potentiometer 250.

If the weight of the first material received in hopper 38 is within theacceptable weight range, relay UEP-S will be energized and relay OEPSwill remain de-energized as previously explained. Consequently, contactsOEP-Sl and UEP-SZ will be closed, but contacts UEP-Sl and OEP- S2 willbe open to prevent a circuit from being completed to energize timerOWA-T.

If, on the other hand, the weight of the first material delivered tohopper 38 is less than the underweight limit of the acceptable range,both relays UEP-S and OEP-S will be de-energized. As a result, contactsOEP-Sl and UEPS1 will be closed to complete a circuit from terminal 330to energize timer OWAT.

If the weight of the first material delivered to hopper 38 exceeds theoverweight limit of the acceptable range, both relays UEP-S and OEPSwill be energized. Under these conditions, contacts OEP-S2 and UEPS2will be closed to complete a circuit from terminal 330 to energize thetimer OWAT.

Following a predetermined time delay after a circuit is completed fortimer OWA-T signifying that the weight of the material is eitheroverweight or underweight, the timer times out to close a set ofcontacts OWA-T1 (FIG. 6) to complete a circuit for illuminating anoff-Weight lamp 332.

Still referring to FIG. 6, relay O'EP-S is provided with a set ofnormally closed contacts DEF-S3 and relay UEP- S is provided with a setof normally open contacts UEP- S3 to control energization of steppercoil SS-C. If the weight of the first material delivered to weigh hopper38 is within the acceptable weight range, contacts OEP-S3 will remainclosed since relay OEPS is de-energized and contacts UEP-S3 will closeowing-to the energization of relay UEP-S. With contacts OEP-S3 and UEPS3both closed, a circuit is completed for energizing stepper coil SS-C.This circuit may be traced from conductor 300 through contacts DS-Tl toterminal 330, from terminal 330 through contacts OEP-S3 and contactsUEPS3, which are connected in series, through a set of normally closedcontacts R-T2 of timer R-T, and through coil SS-C to conductor 301. Whenenergized, stepper coil SS-C closes a set of stepper switch interruptercontacts 340. By closing contacts 340, a circuit is completed forenergizing timer R-T. This circuit may be traced from conductor 300through contacts 340 and through the operating winding for timer R-T toconductor 301.

Energization of timer R-T immediately opens contacts R-TZ to interruptthe energizing circuit for stepper coil SS-C. When stepper coil SSC isenergized, the stepping mechanism of switch 182 is cocked, and when coilSS-C de-energizes by opening contacts R-T2, the cooked stepper mechanismthen advances contact arms 314, 320, 184, and 184a to the next contactin their respective banks of contacts.

In the event that the weight of the first material delivered to hopper38 is not within the acceptable range, a circuit will not be completedto energize stepper coil SS-C since either contacts OEP-S3 or contactsUEP-S3 will be open. Thus, when the weight of a delivered ingredient isnot within the acceptable weight range, automatic operation of theweighing system will stop, requiring the load received in hopper 38 tomanually be discharged and requiring the control circuitry to be resetin a manner to be described later on.

When contact arms 314 and 320 are advanced to their #2 positions inbanks 318 and 324 respectively, no circuit, as yet, will be completedfor energizing relays 2DF and 2FF since energization of timer R-Timmediately opens contacts R-Tl. Opening of contacts R-Tl alsointerrupts the energizing circuits for timers DF-T and DS-T.

When stepper coil SSC is de-energized, contacts 340 open to interruptthe energizing circuit for timer R-T. As a result, timer R-T now startsto time out allowing timers DF-T and DS-T to reset their respectivecontacts. When timer R-T finally times out, timer DF-T and relay TR-Cwill again be energized by the closure of contacts RT1.

Capacitor 210 will now be charged to the increased value of thetransducer output signal E which, at this stage, is steady because nomaterial is being delivered to or removed from weigh hopper 38. Whentimer DF-T times out, contacts DF-Tl open to de-energize relay TR- C.Contacts TR-C1 thereby open and the increased voltage signal sto-red oncapacitor 210 is applied to modules 121, 122, 123, and 125 in the formof voltage signals E in the manner previously described. The algebraicsummation of voltage signals E and E at junctions 140, 160, 140a, and160a will consequently become zero. Since contact arm 184 has now beenadvanced to its second position for developing the voltage correspondingto the desired weight of the second material to be delivered to weighhopper 38, an unbalanced voltage signal condition will be impressed uponcomparators 152, 162, 152a, and 162a.

22 As a result, relays EP-S, DEP-S, UEP-S, and OEP-S will allde-energize to reset their associated contacts.

When contacts DEP-Sl close as a result of de-energizing relay DEP-S, acircuit will be completed through contact arm 320 at its #2 positionwhere it engages the second contact in bank 324 to energize relay 2FFfor starting motor 32a. This energizing circuit may be traced fromconductor 300, through contacts S-R2, through contacts R-Tl (which arenow closed as a result of relay R-T timing out), through contacts DF-TZ(which are now closed as a result of relay DFT timing out), throughcontacts DEP-S1 (which are now closed as a result of deenergizing relayDEPfis), through contact arm 320 and through the winding of relay 2FF toconductor 301.

Concomitantly with the energization of relay 2FF, a circuit will becompleted for energizing relay 2DF for starting motor 48a. This circuitmay be traced from conductor 300 through contacts S-R2, R-Tl, and DF-TZ,through contacts EP-Sl (which are now closed as a result ofde-energizing relay EP-S), through contact arm 314, and through thewinding of relay 2DF to conductor 301.

As shown in FIG. 7, energization of relay 2FF closes normally opencontacts 2FF-1, 2FF-2, and 2FF-3 to start motor 32a. When relay 2FF isenergized, a further set of normally open contacts 2FF-4 are also closedto complete a circuit for energizing solenoid 76a.

Energization of relay 2DF closes normally open contacts 2DF-1, 2DF-2,2DF-3, and 2DF-4 for energizing motor 48a and solenoid a.

By energizing motors 32a and 48a and by energizing solenoids 76a and80a, it is clear that feeders 60 and 62 will be started and that catchgates 73a, and 77a will be opened, thus providing for the delivery ofthe second material to weigh hopper 38. The second material will thus befed at a full flow rate to weigh hopper 38, and the transducer outputvoltage signal E will thus increase until a balanced signal condition isobtained at comparator 152. The signal output of comparator 152 willthen energize relay DEP-S as previously explained. Energization of thisrelay opens contacts D'EP-Sl to interrupt the energizing circuit forrelay 2FF. De-energization of relay 2FF opens contacts 2FF-1, 2FF-2,2FF-3, and 2FF-4 to deenergize motor 32a and also to de-energizesolenoid 76a. Consequently, feeder 60 will stop and gate 73a will beswung to its flow-interrupting, closed position.

The second material will now be fed to hopper 38 at a reduced, dribblefeed rate by feeder 62, thereby causing the transducer output voltagesignal to continue to increase. When the final cutoff point is reached,as determined by the setting of potentiometer arm,175a, the balancedvoltage signal condition biases diode 163 forwardly to re-energize relayEP-S.

Energization of relay EP-S opens contacts EP-Sl to interrupt theenergizing circuit for relay 2DF. De-energization of relay 2DF openscontacts 2DF-1, 2DF-2, 2DF-3, and 2DF-4 to de-energize motor 48a andalso to de-energize solenoid 80a. As a result, catch gate 77a will closeand feeder 62 will stop to discontinue the delivery of the secondmaterial to hopper 38.

Contacts EP-SZ which are closed by re-energizing relay EP-S completes acircuit for again energizing timer DST for allowing the scale tostabilize before checking the weight of the second material with network332. Once timer DS-T times out, network 332 becomes operative in thepreviously described manner to check if the weight of the secondmaterial delivered to hopper 38 is within the acceptable toleranceestablished by the settings of potentiometers 148a and 250.

If the Weight of the second material is within the acceptable tolerance,a circuit will be completed through contacts OER-S3 and UEPS3 toenergize stepper coil SS-C in the manner already explained. This closesthe stepper switch interrupter contacts 340 to energize timer R-T whichimmediately de-energizes coil SS-C to advance contact arms 314, 320,184, and 184a to the third contact position in their respective contactbanks. In addition, timers DF-T and DS-T are reset to the de-energizedstate.

Timer R-T now times out again to energiez timer DF- T and also relayTR-C as previously explained. When timer DF-T times out, contacts DFT1open to de-energize relay TR-C and contacts DF-T2 close completing acircuit up to the third contact in each of the banks 318 and 324.However, no circuit will be completed through these contact arms sincethere are no motor-starter relays connected to the third contactpositions in banks 318 and 324.

At this stage, a circuit will be completed through a further contact arm350 (see FIG. 6) to energize a homestepper relay HSR. Contact arm 350 iscontained in a further deck 352 forming a part of switch 182 andcomprising a bus 354 and a series of electrically independent contactsin a bank 356. Contact arm 350 is connected to bus 354 and isadvanceable to successively engage the contacts in bank 356. The numberof contacts in bank 356 is the same as the number of contacts in thepreviously described contact banks of switch 182. Contact arm 350 isganged to arms 314, 320, 184, and 184a to move in synchronism therewith.In deck 352, the contact positions 1, 2, and 4-10 are open circuits, andpositions 3 and 11 are connected to provide a homing circuit as will nowbe described.

Since the first and second positions in bank 356 are open circuits, nocircuit will be completed through contact ar'm 350 during the deliveryof the first and second materials. However, when the delivery of thesecond material to weigh hopper 38 is completed, and when contact arm350 is advanced to its third position in bank 356 along. with theadvancement of the other stepper switch contact arms, a circuit will becompleted for energizing relay HS-R. This energizing circuit may betraced from conductor 300 through contacts S-R2 and R-Tl, through arm350 to the third contact in bank 356, and through the winding of relayHSR to conductor 301.

When relay HSR is energized, it closes a normally open set of contactsHS-Rl which establishes a holding circuit. This holding circuit may betraced from a conductor 301 through the winding of relay HS-R, throughcontacts HS-Rl, and through a set of normally closed stepper switchcontacts SSCl which are operated by the stepper network 329. Thus, relayHS-R can only be de-energized by opening contacts SSCI. As will becomeapparent, contacts SSCl will open only when contact arm 350 is steppedto the last contact position in bank 356.

Energization of relay HSR closes a second set of normally open contactsHSR2 to complete a new energizing circuit for stepper coil SSC. Thiscircuit may be traced from conductor 300, through contacts SS-Cl,through a further set of normally closed interrupter stepper switchcontacts SS-C2, through contacts HS-R2, and through coil SSC toconductor 301.

Energization of coil SSC opens contacts SSC2 to de-energize the steppercoil for advancing contact arms 314, 320, 350, 184, and 18411 to thefourth contact position in their respective contact banks. Relay HS-Rwill remain energized through contacts SSCl. When coil SSC de-energizes,contacts SSCZ close to re-energize coil SSC. The contact arms 314, 320,350, 184, and 184a will now be stepped in this self-interrupting fashionuntil contact arm 350 engages the last contact in bank 356.

When contact arm 350 engages the last contact in bank 356, contacts SSC1will open to interrupt the relay holding circuit through contacts HS-Rl,causing relay HS-R to de-energize and thereby holding contact arms 314,320, 350, 184, and 184a at the last contact positions in theirrespective contact banks.

When contact arm 350 engages the last contact in bank 356 and whencontacts R-Tl close, a circuit is completed for energizing a dischargerelay DR. This circuit may be traced from conductor 300, throughcontacts S-RZ and RT1, through arm 350 to the eleventh or last contactin bank 356, and through the winding or relay D-R to conductor 301.Energization of relay D-R closes a set of normally open contacts DR1 tocomplete an energizing circuit for a slow drop-out discharge timer D-T.The operating winding of timer D-T is connected in series with contactsDR1 across conductors 300 and 301.

By operating timer D-T, a set of contacts D-T1 are closed to complete acircuit for energizing solenoid 72 which opens discharge gate 66 todischarge the material delivered to hopper 38. Operation of timer D-Tinstantaneously closes a set of normally open contacts D-T2 to completeanother energizing circuit for stepper coil .SS-C. This circuit may betraced from conductor 300, through contacts DT2, through contacts R-T2,and through stepper coil SSC to conductor 301.

As a result of energizing coil SSC, contacts 340 will close to completean energizing circuit for timer R-T. In this time, discharge gate 66will be opening and will activate limit switch 306 to its open position,with the result that relay S-R will be de-energized. By de-energizingrelay S-R, contacts S-R1 and S-R2 will open to de-activate the part ofthe control circuit controlled through contacts SR2.

As a result of energizing relay R-T, contacts R-T2 will open aspreviously explained to interrupt the energizing circuit for steppercoil SSC. This causes contacts 340 to open to interrupt the energizingcircuit for timer RT which then starts to time out, thereby advancingcontact arms 314, 320, 350, 184, and 184a to the first contact positionin their respective contact banks. No feeding of material will occur,however, since relay S-R will have been de-energized by the time timerR-T times out.

After timer D-T times out and limit switch 306 closes, indicating thatdischarge gate 66 is closed, the control circuit will be reset foranother feeding cycle.

When the condition of a weighing of any one of the materials deliveredto hopper 38 is off-weight and consequently not within the overweight ofunderweight tolerance limits set by potentiometers 148a and 250,automatic operation of the weighing system will be interrupted because,as previously explained, either contacts OEP-S3 or contacts UEP-S3 willbe open, thereby preventing a circuit from being completed forautomatically energizing stepper coil SSC to advance the contact arms ofswitch 182 to their next contact positions in their respective contactbanks. Under such conditions, contacts OWA-Tl will be closed toilluminate lamp 332 and also to complete a circuit to one terminal of aby-pass off-weight and discharge switch 360 shown in FIG. 6. Withcontacts OWA-T1 closed, switch 360, which may be of the spring-loaded,push-button type, must be depressed by the operator in order todischarge the contents in hopper 38 before another weighing cycle can beinitiated. By depressing switch 360, a circuit is completed forenergizing a relay BW-R. This circuit may be traced from conductor 300,through contacts OWAT1, through switch 360, and through the operatingwinding of relay BW-R to conductor 301.

Energization of relay BW-R closes two sets of normally open contactsBW-R1 and BW-R2. Closing of contacts BW-Rl establishes a holding circuitaround switch 360 to keep relay BW-R energized when switch 360 isreleased. Closing of contacts BW-R2 completes an energizing circuit foroperating stepper coil SSC. Energization of coil SSC opens contactsSS-C2 to interrupt the energizing circuit through contacts BW-R2, withthe result that all of the contact arms of switch 182 'will be advancedto their next contact positions in their respective contact banks. Byde-energizing coil SSC, contracts SS-CZ again close to re-energizestepper coil SSC in the manner previously explained. Accordingly, coilSSC will be pulsed to step the contact arms of switch 182 in thisself-interrupting fashion until contact arm 350 engages the last contactin bank 356.

By engaging contact arm 350 with the last contact in bank 356, contactsSS-Cl will now open to interrupt the relay holding circuit throughcontacts BW-Rl. As a result, relay BW-R will de-energize, causingcontacts BW- R1 and BW-R2 to open. This de-activates the stepper switchnetwork 329 with all of the contact arms of control switch 182 at theirlast contact positions in their respective contact banks. Finally, aspreviously explained, the discharge cycle is started, commencing withthe energization of relay D-R to discharge the contents of hopper 38 andto reset the circuit for another weighing cycle.

As shown in FIG. 6, a further spring-loaded pushbutton set and resetswitch 370 is connected in series with switch 360' between conductors300 and 301. By simultaneously depressing switches 360 and 370, relayBW-R is energized for stepping the contact arms of switch 182 to theirfirst contact positions in their respective contact banks. Switch 370 isused only after a power failure or during initial start-up to positionthe contact arms of switch 182 for a weighing cycle whenno material isin hopper 38.

If module 121 is replaced with module 270-, relays lFF and ZFF may bepermanently disconnected from the circuit or contacts DEF-S1 may beplaced under the control of relay EP-S. If module 122 is removed,contacts UEP-S3 must be jumped and timer OWA-T may permanently bedisconnected from the circuit.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A weighing system comprising means for delivering material to beweighed to a receptacle, weight sensing means for developing a firstelectrical signal representative of the weight of material delivered tosaid receptacle, means for developing a second electrical signalrepresenting the selected weight of material desired to be delivered tosaid receptacle, control means having at least two input terminals, andmeans for impressing-said first and second signals on respective ones ofsaid input terminals, said control means further comprising electricalcircuit completing and printed circuit module receptacle means, at leasttwo separately formed printed circuit modules adapted to be removablyplugged into said electrical receptacle means independently of eachother, means forming a part of said circuit completing and receptaclemeans and connected to said terminals to provide separate current pathsfor applying each of said signals to each module, signal comparingcircuits on said modules and being coupled to each input terminalindependently of each other by respective ones of said current pathswhereby the removal of one of said modules from said circuit completingand receptacle means does not aifect the performance of the circuit onthe other of said modul es, each of said circuits being operative to atleast compare said first signal with said second signal, and signalutilization means coupled through said circuit completing and receptaclemeans to each circuit and being controlled by said comparison.

2. A weighing system comprising means for delivering material to beweighed to a receptacle, weight sensing means operatively associatedwith said receptacle for developing a first electrical signalrepresentative of the weight of material delivered to said receptacle,means for developing a second electrical signal representing theselected weight of material desired to be delivered to said receptacle,electrical circuit completing and printed circuit module receptaclemeans, means operatively connecting said first and second signaldeveloping means to said circuit completing and printed circuit modulereceptacle means for impressing said first and second signals on thecircuit completing portion of said circuit completing and printedcircuit module receptacle means, at least two separately formed printedcircuit modules adapted to be removably plugged into said circuitcompleting and printed circuit module receptacle means independently ofeach other, printed signal comparing means on each of said modules,means forming a part of said circuit completing and receptacle means andproviding current paths for applying each of said signals to the signalcomparing means on each module, said cur rent paths being formedindependently of each other to provide for the application of saidsignals to the signal comparing means of either of said modules evenwhen the remaining one of the modules is removed from said circuitcompleting and printed circuit module receptacle means, the signalcomparing means on one of said modules comprising a circuit forproducing a first output signal when said first signal reaches apredetermined value relative to said second signal, said means fordelivering said material being responsive to said first output signalfor interrupting the delivery of material to said receptacle, means fordeveloping a preset electrical signal, the signal comparing means on theother of said modules comprising a circuit responsive to said first,second and preset signals for producing a second output signal when theweight of material delivered to said receptacle deviates from saidselected weight by a magnitude determined by said preset signal, andsignal utilization means operatively connected to the signal comparingmeans on said other module and being controlled by said second outputsignal.

3. A weighing system comprising means for delivering material to beWeighed to a receptacle, weight sensing means operatively associatedwith said receptacle for developing a first electrical signalrepresentative of the weight of material delivered to said receptacle,means for developing a second electrical signal representing theselected Weight of material desired to be delivered to said receptacle,electrical circuit completing and printed circuit module receptaclemeans, means operatively con necting said first and second signaldeveloping means to said circuit completing and printed circuit modulereceptacle means for impressing said first and second electrical signalson the circuit completing portion of said circuit completing and printedcircuit module receptacle means, printed circuit module means connectedto said circuit completing and printed circuit module receptacle meansand including at least two separately formed circuits, means forming apart of said circuit completing portion for simultaneously applying saidfirst electrical signal to both of said circuits and for applying saidsecond electrical signal at least to one of said circuits, means fordeveloping a selectively preset electrical signal and for applying saidpreset signal to the other of said circuits, means forming a part ofsaid one of said circuits for comparing at least said first and secondsignals, said means for delivering said material to said receptaclebeing operatively connected to said one of said circuits and beingresponsive to the comparison of at least said first and secondelectrical signals for interrupting the delivery of material to saidreceptacle when said first electrical signal reaches a predeterminedvalue relative to said second electrical signal, means forming a part ofsaid other of said circuits for comparing at least said first and presetsignals and signals utilization means responsive to the comparison of atleast said first and preset signals for providing a signal when theweight of material delivered to said receptacle deviates from saidpreselected weight by an amount determined by the value of said presetsignal.

4. A weighing system comprising a weighing receptacle, means providingfor the successive delivery of at least two separate materials to saidreceptacle, weight selection means for pre-setting the desired amountsof said first and second materials to be delivered to said receptacle,electrical circuit completing and printed circuit card support means, aprinted circuit card having circuit means and being removably pluggedinto said circuit completing and card mounting means, control meansoperatively connected to said weight selection means, to saidreceptacle, and through said electrical circuit completing means to saidcard for applying predetermined voltage signal conditions to saidcircuit means, said circuit means being responsive to said signalconditions for developing an output signal, and said delivery meansbeing controlled by said output signal to sequentially deliver saiddesired amounts of said first and second materials to said Weighingreceptacle.

5. The weighing system defined in claim 4 wherein said circuit meanscomprises a voltage comparison circuit having an operational amplifierproviding said output signal, an electrical summing junction connectedat one of the input terminals of said amplifier, resistor means couplingsaid signal condition to said junction, and a feedback loop connectedbetween said junction and the output of said amplifier and containing aZener diode, poled to control voltage at the output of said amplifier inresponse to a change in said signal conditions between balanced andunbalanced states.

6. A weighing system comprising means for delivering material to areceptacle, means for developing a first electrical signalrepresentative of the weight of material delivered to said receptacle,means for developing a second electrical signal which is selectivelypreset for representing the desired weight of material to be deliveredto said receptacle, printed circuit module interconnection means havingfirst, second and third terminal means, a printed circuit moduleremovably mounted on said module interconnection means for electricalconnection with said first, second, and third terminal means, means forcoupling said first and second signals respectively through said firstand second terminal means to said module, said module having signalcomparing circuit means for developing an output signal responsive tothe algebraic summation of at.

least said first and second signals, signal utilization means, and meanscoupling said output signal through said third terminal means to controloperation of said utilization means.

7. The weighing system defined in claim 6 wherein said utilization meansis actuated by a predetermined value of said output signal to reduce theflow rate of material being delivered to said receptacle, said weighingsystem furthercomprising means for developing a third electrical signalwhich is selectively preset, fourth terminal means on said moduleinterconnection means, and means for coupling said third signal throughsaid fourth terminal means to said module, said circuit means beingoperative to compare said second signal with the sum of said first andthird signals for providing said output signal with said predeterminedvalue before the weight of material delivered to said receptacle becomesequal to said desired weight.

8. The weighing system defined in claim 6 comprising means fordeveloping a third electrical signal which is selectively preset, fourthterminal means disposed on said module interconnection means and beingelectrically connected to said module, and means for coupling said thirdsignal through said fourth terminal means to said circuit means, saidoutput signal being responsive to the algebraic summation of at leastsaid first, second, and third signals to reach a predetermined valuewhen the weight of material delivered to said receptacle deviates fromsaid desired weight by at least a predetermined amount, said utilizationmeans being actuated when said output signal attains said predeterminedvalue to provide an indication of the weight deviation.

9. The weighing system defined in claim 6 wherein said utilization meansis actuated when said output signal reaches a predetermined magnituderepresenting a balanced signal condition for interrupting the deliveryof the material to said receptacle.

10. The weighing system defined in claim 9 comprising fourth terminalmeans on said module interconnection means and being electricallyconnected to said module, means for developing a third electrical signaland for coupling said third signal through said fourth terminal means tosaid circuit means, said circuit means being operative to compare saidsecond signal with the sum of said first and third signals fordeveloping said balanced signal condition before the weight of materialreceived in said receptacle becomes equal to said desired weight.

11. A weighing system comprising a weighing receptacle, means providingfor the successively delivery of at least first and second materials tosaid receptacle, transducer means operatively associated with saidreceptacle for developing a first voltage signal representative of theweight of material delivered to said receptacle, means for developing atleast second and third voltage signals which are selectively preset torespectively and nonaccumulatively represent the desired weights of saidfirst and second materials to be delivered to said receptacle, meansmemorizing said first signal before each of said materials is deliveredfor developing a fourth signal representing the weight of material insaid weighing receptacle before each of said first and second materialsis delivered, electrical circuit completing and printed circuit modulemounting means, a printed circuit module removably mounted on saidcircuit completing and mounting means, means for coupling said first andfourth signals through said circuit completing and mounting means tosaid module at least during the delivery of each of said first andsecond materials, means for operating said delivery means tosequentially deliver said first and second materials to said weighingreceptacle and for sequentially coupling said second and third signalsthrough said circuit completing and mounting means to said modulerespectively during the delivery of said first and second materials,voltage comparing means on said module for first comparing said secondsignal with the difference in magnitudes between said first and fourthsignals and then comparing said third signal with the difference inmagnitudes between said first and fourth signals, and means responsiveto said comparisons for controlling the delivery of said first andsecond materials to said weighing receptacle.

12. The weighing system defined in claim 11 wherein said memorizingmeans comprises a further printed circuit module removably mounted onsaid circuit completing and module mounting means.

13. The weighing system defined in claim 11 comprising a further printedcircuit module removably mounted on said circuit completing and modulemounting means and being operatively connected to said second and thirdsignal developing means and said memorizing means for providing anindication whenever the weight of material to be delivered to saidweighing receptacle exceeds a predetermined amount when added to theWeight of any material already in said weighing receptacle.

14. The weighing system defined in claim 11 comprising a further printedcircuit module removably mounted on said circuit completing and modulemounting means, means for coupling said first, second, third, and fourthsignals through said circuit completing and module mounting means tosaid further module concomitantly with application of said first,second, third, and fourth signals to said comparing means, meanscoacting with said first and second signals to establish a predeterminedvoltage signal condition on said further module whenever the 29 weightof either of said first and second materials deviates from the desiredweight by at least a predetermined amount. I

15. The weighing system defined in claim 11 wherein said means couplingeach of said second and third signals to said module comprises a devicewhich is selectively operable to proportionately vary the magnitudes ofsaid preset signals.

16. The weighing system defined in claim 15 wherein said devicecomprises a potentiometer and wherein said means coupling said secondand third signals to said circuit means further comprises a printedvoltage follower circuit module removably mounted on said circuitcompleting and module mounting means and providing a part of a currentpath between said potentiometer and said comparing means.

References Cited UNITED STATES PATENTS 1 RICHARD B. WILKINSON, PrimaryExaminer 0 G. H. MILLER, JR., Assistant Examiner US. Cl. X.R.

